The present invention generally relates to fabrication of semiconductor devices and more particularly to a fabrication process of a semiconductor device including a dicing process and a construction of a dicing blade used therefore.
In the fabrication of a semiconductor device, a number of semiconductor device patterns are formed on a single semiconductor wafer, wherein the semiconductor wafer thus formed with the device patterns is subjected to a dicing process in which the semiconductor wafer is divided into individual semiconductor chips. In the dicing process, a rotary dicing blade is used for sawing the semiconductor wafer along a predetermined dicing line defined on the semiconductor wafer.
In such a fabrication process of a semiconductor device, it is required to reduce the width of the dicing line as much as possible so as to maximize the number of the semiconductor chips obtained from a single semiconductor wafer. Further, in order to maximize the throughput of production, it is desired to maximize the feeding speed of the rotary dicing blade on the semiconductor wafer along the dicing line.
FIGS. 1A and 1B are diagrams showing the construction of a conventional rotary dicing blade 10 used in a conventional dicing process, wherein FIG. 1A shows the dicing blade 10 in a side view while FIG. 1B shows the dicing blade 10 in a front view. Further, FIG. 1C shows the dicing blade 10 in an enlarged view.
Referring to FIGS. 1A and 1B, the rotary dicing blade 10 includes a rotary hub 11 of an Al alloy and a blade edge 13 of Ni or a Ni alloy, wherein the hub 11 is formed with a hole 12 for accepting a rotary drive shaft of a dicing machine (not shown). Further, the blade edge 13 is formed along an outer circumference of the hub 11. As indicated in the enlarged view of FIG. 1C, the blade edge 13 carries thereon diamond abrasive particles.
FIG. 2 shows a Si wafer 15 that is to be diced by the rotary dicing blade 10.
Referring to FIG. 2, a number of semiconductor chips 16 are defined on the Si wafer 15 by criss-crossing dicing lines 17, and the foregoing rotary dicing blade 10 saws the wafer 15 along the dicing lines 17. It should be noted that each semiconductor chip 16 includes a number of semiconductor elements (not shown) therein and forms an integrated circuit.
FIG. 3 shows an example of dicing the Si wafer 15 along a dicing line 17 of FIG. 2 by the rotary dicing blade 10 of FIGS.1A-1C.
Referring to FIG. 3, the dicing line 17 has a width w of about 150 .mu.m, and a dicing groove 17A having a width corresponding to a width W of the blade edge 13 is formed inside the dicing line 17. In a typical example, the blade edge 13 has an edge length L of about 700 .mu.m and an edge width W of about 60 .mu.m. The blade edge 13 carries, on a circumferential surface and on both lateral surfaces thereof, diamond abrasive particles 14 having a grain size of 4-8 .mu.m. The diamond abrasives 14 may be electro-deposited on the blade edge 13.
As can be understood from FIG. 3, the dicing groove 17A thus formed by the rotary dicing blade 10 is defined by irregular side walls 18. The projections and depressions thus formed on the side walls 18 is called a "chipping" and are designated by .DELTA.. Thus, in order to minimize the width w of the dicing line 17, it is necessary to minimize the chipping .DELTA. also. In the case of a dicing process conducted by the rotary dicing blade 10 of the foregoing construction, it is necessary to set the feeding speed of the blade 10, in other words the relative speed of the rotary dicing blade 10 with respect to the semiconductor wafer 15, to be less than 100 mm/sec in order to suppress the chipping .DELTA. below about 30 .mu.m. However, the use of such a low feeding speed of the dicing blade 10 inevitably raises the problem of reduced throughput of production of the semiconductor device. Further, the use of such a low feeding speed for the dicing blade causes a problem of reduced lifetime of the blade 10 because of the increased time needed for completing one dicing pass. In the case of dicing a Si wafer of a six inch diameter, fifty-thousand passes are considered the maximum lifetime of the blade 10.
In the construction of FIG. 3, it has been necessary to reduce the edge length L of the rotary dicing blade 10 to about 500 .mu.m when the width w of the dicing line 17 is going to be reduced to about 90 .mu.m. In correspondence to this, it has been necessary to reduce the edge width W to about 45 .mu.m. Further, it has been necessary to reduce the feeding speed of the blade 10 to below about 60 mm/sec in order to suppress the chipping .DELTA. below about 20 .mu.m. Thereby, the throughput of production of the semiconductor device is reduced further. Further, because of the increased time needed for one dicing pass as a result of the reduced feeding speed of the rotary dicing blade, the lifetime of the rotary dicing blade 10 of the foregoing construction is reduced to about thirty thousand passes in the case of dicing a six inch Si wafer.
While it may be possible to increase the lifetime of the rotary dicing blade by increasing the edge length L of the blade edge 13, such an approach tends to invite a problem of increased degree of deflection or deformation of the blade edge 13. Thereby, the reduction of the feeding speed of the rotary dicing blade is inevitable. For example, the feeding speed has to be suppressed below 70 mm/sec.